Proteomic identification of glycosylphosphatidylinositol anchor-dependent membrane proteins elevated in breast carcinoma.

The glycosylphosphatidylinositol (GPI) anchor is a lipid and glycan modification added to the C terminus of certain proteins in the endoplasmic reticulum by the activity of a multiple subunit enzyme complex known as the GPI transamidase (GPIT). Several subunits of GPIT have increased expression levels in breast carcinoma. In an effort to identify GPI-anchored proteins and understand the possible role of these proteins in breast cancer progression, we employed a combination of strategies. First, alpha toxin from Clostridium septicum was used to capture GPI-anchored proteins from human breast cancer tissues, cells, and serum for proteomic analysis. We also expressed short interfering RNAs targeting the expression of the GPAA1 and PIGT subunits of GPIT in breast cancer cell lines to identify proteins in which membrane localization is dependent on GPI anchor addition. Comparative membrane proteomics using nano-ESI-RPLC-MS/MS led to the discovery of several new potential diagnostic and therapeutic targets for breast cancer. Furthermore, we provide evidence that increased levels of GPI anchor addition in malignant breast epithelial cells promotes the dedifferentiation of malignant breast epithelial cells in part by increasing the levels of cell surface markers associated with mesenchymal stem cells.

A unique benign mucinous cystadenoma of the retroperitoneum: a case report and review of the literature.

Primary retroperitoneal mucinous cysts are rare. Most often malignant, lesions present on a spectrum, fitting the histopathological categories of benign, borderline and malignant. The rarest form is the benign mucinous cystadenoma adenocarcinoma, of which only 20 cases have been reported. We present here the curious case of a 37-year-old woman with two large, fast growing, cystic, benign, primary retroperitoneal mucinous cystadenomas treated definitively by local resection.